1873.] DR. J. S. BOWERBANK ON THE SPONGIAD^E. 323 



Hab. Fiji Islands (Sir E. Home). In the collection of the Royal 

 College of Suvgeons (see 'Catalogue of Porifera,' part i. I860, 

 p. 127, B. 170), 



Examined in the dried state. 



The form of this sponge is somewhat like that of a pear, the 

 basal end being the smaller one. It is 2\ inches in height, and 1^- 

 inch at its greatest diameter. The natural base of the sponge is not 

 present. The fractured termination is nearly circular, and is j of 

 an inch in diameter ; and there is every appearance of its having 

 been supported, when perfect, on a short stout pedicel. The surface 

 is armed with numerous minute acerate or fusiformi-acerate spicula, 

 which project from it about one third or half their length at right 

 angles to its plane. The surface of the sponge in its present state 

 has a large number of orifices, produced by the contraction of the 

 tissues ; the true oscula visible are very small, of an oval form, not 

 exceeding above a line in length and half a line iu width, and are 

 closed by the proper membrane of the organ. Immediately beneath 

 the dermal membrane there is a thick stratum of membranous tissue 

 and sarcode, in which the triradiate heads of the connecting-spicuia 

 are immersed. I could not detect in this stratum the slightest 

 indication of the presence of gemmules. The dermal membrane is 

 crowded with the subtuberculated fusiformi- cylindrical spicula ; and 

 very few indeed of the pores were in an open condition. Some of 

 these appeared to have intermarginal cavities beneath them some- 

 what resembling those apparent in the dermal crust of Geodia and 

 Pachymatisma ; but I could not satisfactorily determine the fact of 

 their existence, the tissues in which they are situated having been 

 greatly disarranged by the contraction incurred by drying; under 

 more favourable circumstances it is very probable that such inter- 

 marginal cavities will be found to exist. 



This sponge exhibits in its structure very nearly the extremes in 

 magnitude of the spicula. While those of the skeleton and con- 

 necting system are more than usually large and stout, the defensive 

 ones and those of the membranous and sarcodous systems are 

 unusually minute, and the stellate ones especially so, requiring a 

 linear power of not less than 800 or 1000 to demonstrate their 

 forms in a satisfactory manner : many of them do not exceed ^Vti 

 inch in extreme diameter ; and the fusiformi-cylindrical spicula 

 average jttVif m l en g tn by Yff&o"o mc ^ greatest diameter. 



The interstitial membranes are abundantly covered with sarcode, 

 in which there are a vast number of spherical nucleated cells, 

 varying in diameter from y-gjg-g- inch to xo"oo~o bach. 



Ecionemia densa, Bowerbank. (Plate XXX.) 

 Sponge massive or subcyathiform, sessile ; surface sinuous and 

 uneven, asperated. Oscula simple, dispersed. Pores inconspicuous. 

 Dermal membrane thin, pellucid, abundantly spiculous ; spicula 

 tuberculated, subcylindrical, occasionally fusiform, short and minute. 

 Skeleton-fasciculi numerous and large; spicula fusiformi-cylindrical, 

 long and stout, variable in form and proportion. Connecting-spicuia 



21* 



